Andrea wakes me in the middle of the flight, in the middle of the night, and tells me to come and see the mountains.

We’re just over the halfway stage of a 10-hour flight from Heathrow to Bangkok. I come back to life slowly, having been half asleep listening to music (Gil Scott Heron's Winter in America, which for some reason spooks me and gives me trippy, unsettling dreams). The cabin looks the way all long-haul flights look at the halfway stage – dead bodies in various poses scattered to the left and right, some with headphones, some with books spread open on their chests, some with eyeshades, with mouths agape, hunched in positions that you know they’ll regret in the days to come.

I’m groggy in the extreme. My brain can just about stand long haul flights - it’s my arse that gives me the problems. Despite the relatively comfortable seats provided by Royal Thai airlines, it feels like I’ve been sitting on a concrete block in the bed of a pickup truck coming up the Glenshane Pass for two and a half hours. I’m kind of glad to get up and walk around.

It’s almost completely dark in the cabin, with the occasional glow here and there of a laptop or a reading light. I’ve kicked off my shoes, and the pair of us pick our way gingerly up the aisle to the back of the plane. We stand near a little fold-down seat that is reserved for crew members. There are sleeping passengers all around us, and the lovely Thai cabin crew moving around among them in graceful silence. We must be close to the outside of the fuselage here, or there’s some air conditioning unit below – I can feel the cold under my feet through my socks.

Look at this, she says, and she lifts the window shade – blinding daylight floods in. I had totally forgotten that outside, of course, it’s broad daylight. Still on London time, it’s half past three in the morning and the crew have pulled down all the shades to create an artificial nighttime so we can sleep and arrive refreshed.

But outside the sun is blazing down on an extraordinary landscape. It’s a vast mountain range, capped with snow, shading down to deep sandy plains below, where wide, slow muddy rivers make their way across vast distances.

We ponder where we might be, and can only conclude that we must be over one of the ‘Stans’ - Uzbekistan, Afghanistan, Kurdistan, Pakistan... or perhaps Kashmir. In the distance we can see the icy contours of what logically must be the foothills of the Himalayas. It’s magical, this landscape below us, rumpled and veined - like silver paper used to be when you unwrapped chocolate bars in childhood.

After a while, we begin to see what look like settlements below, but we can’t determine their use – we can make out lots of little square structures, perhaps enclosures for sheep or cattle, lots of them clustered together. From here they look like little desk staples fallen onto spilled cocoa powder. Occasionally there is the glint, from a corrugated iron roof, perhaps. We take some pictures through the cabin window, and resolve to check the maps when we get a moment, and try and work out what we’ve seen.

We pull down the shade, and make our way in almost total blindness back to our seats, dazzled by the sunshine on snow and the bright band of clouds in the distance to the north. There are still four hours to go...